The Himalaya-Hengduan mountainous regions locate in southwest China, which forming the south-eastern part of the Qinghai-Tibet Plateau and adjacent from the west to the Sichuan Basin. The elevations of these regions are from 1,300 to 6,000 meters and most of the areas are covering by dense, pristine forests. Attribute to its relative isolation and the fact that most of the area remained free from glaciation during ice ages; the regions have become a very complex habitat with high degree of biodiversity. Beside of as the hometown of the rare and endangered Giant Panda, the Himalaya-Hengduan mountainous regions have been considered as the major players of species distributions and genetic diversities of Southwest China.
To discover the mysteries of regional geography historic events and climate changes to biology genetic diversities, Ph.D candidate LIU Qi (the Kunming institute of Zoology, the CAS) and his colleagues have conducted a systematic research by choosing Apodemus as the model animal.
Apodemus species are among the most common small rodents inhabiting woodlands and forests of the Palaearctic and Oriental Region. There are 12 extant Apodemus species in the Oriental Region, but only four forms are reported from the Eastern Trans-Himalayas. Among them, the Apodemus draco complex include A. draco, A. ilex, and A. orestes and are distributed in mountain areas in China, Myanmar, and India. But the taxonomic status of A. draco and A. ilex are still controversial. Based on those backgrounds, by investigating fossil collections and geographic records, LIU and his colleagues have collected 203 A. draco complex samples from 51 sampling sites across the Himalaya-Hengduan mountainous regions. And, the complete cytochrome b gene sequences (cyt-b) of those samples have also been determined.
In this study, by adopting phylogenetic and phylogeographical approaches, the different revisions regarding the taxonomic status of A. ilex, the effect of the complex geological structures in the Himalayan regions on the genetic diversity of A. ilex, as well as the hypotheses of the biogeographic patterns and colonization history of A. ilex have been determined. In addition, a Bayesian method with a ‘‘relaxed’’ clock model was applied to co-estimate the phylogenetic relationships and divergence times of Apodemus.
According to LIU, A. ilex is a valid species rather than synonym of A. draco. As a middle-high elevation inhabitant, the phylogenetic pattern of A. ilex was strongly related to the complex geographical structures in southwest China, particularly the existence of deep river valley systems, such as the Mekong and Salween rivers. Also, it appears that the evolutionary history of A. ilex, such as lineage divergences and population expansions were strongly affected by climate fluctuation in the Late Pleistocene.
The main findings of this study have been published on PLoS One (http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0031453).
